The present invention relates to compounds that are S1P1 receptor agonists having at least immunosuppressive, anti-inflammatory, and/or hemostatic activities, e.g. by virtue of modulating leukocyte trafficking, sequestering lymphocytes in secondary lymphoid tissues, and/or enhancing vascular integrity.
The present application is in part focused on addressing an unmet need for immunosuppressive agents such as may be orally available which have therapeutic efficacy for at least autoimmune diseases and disorders, inflammatory diseases and disorders (e.g., acute and chronic inflammatory conditions), transplant rejection, cancer, and/or conditions that have an underlying defect in vascular integrity or that are associated with angiogenesis such as may be pathologic (e.g., as may occur in inflammation, tumor development, and atherosclerosis) with fewer side effects such as the impairment of immune responses to systemic infection.
The sphingosine-1-phosphate (S1P) receptors 1-5 constitute a family of G protein-coupled receptors with a seven-transmembrane domain. These receptors, referred to as S1P1 to S1P5 (formerly termed endothelial differentiation gene (EDG) receptor-1, -5, -3, -6, and -8, respectively; Chun et al., Pharmacological Reviews, 54:265-269, 2002), are activated via binding by sphingosine-1-phosphate, which is produced by the sphingosine kinase-catalyzed phosphorylation of sphingosine. S1P1, S1P4, and S1P5 receptors activate Gi but not Gq, whereas S1P2 and S1P3 receptors activate both Gi and Gq. The S1P3 receptor, but not the S1P1 receptor, responds to an agonist with an increase in intracellular calcium.
S1P receptor agonists having agonist activity on the S1P1 receptor have been shown to rapidly and reversibly induce lymphopenia (also referred to as peripheral lymphocyte lowering (PLL); Hale et al., Bioorg. Med. Chem. Lett., 14:3351-3355, 2004). This is attended by clinically useful immunosuppression by virtue of sequestering T- and B-cells in secondary lymphoid tissue (lymph nodes and Peyer's patches) and thus apart from sites of inflammation and organ grafts (Rosen et al., Immunol. Rev., 195:160-177, 2003; Schwab et al., Nature Immunol., 8:1295-1301, 2007). This lymphocyte sequestration, for example in lymph nodes, is thought to be a consequence of concurrent agonist-driven functional antagonism of the S1P1 receptor on T-cells (whereby the ability of S1P to mobilize T-cell egress from lymph nodes is reduced) and persistent agonism of the S1P1 receptor on lymph node endothelium (such that barrier function opposing transmigration of lymphocytes is increased) (Matloubian et al., Nature, 427:355-360, 2004; Baumruker et al., Expert Opin. Investig. Drugs, 16:283-289, 2007). It has been reported that agonism of the S1P1 receptor alone is sufficient to achieve lymphocyte sequestration (Sanna et al., J Biol. Chem., 279:13839-13848, 2004) and that this occurs without impairment of immune responses to systemic infection (Brinkmann et al, Transplantation, 72:764-769, 2001; Brinkmann et al., Transplant Proc., 33:530-531, 2001).
That agonism of endothelial S1P1 receptors has a broader role in promoting vascular integrity is supported by work implicating the S1P1 receptor in capillary integrity in mouse skin and lung (Sanna et al., Nat Chem. Biol., 2:434-441, 2006). Vascular integrity can be compromised by inflammatory processes, for example as may derive from sepsis, major trauma and surgery so as to lead to acute lung injury or respiratory distress syndrome (Johan Groeneveld, Vascul. Pharmacol., 39:247-256, 2003).
An exemplary S1P receptor agonist having agonist activity on the S1P1 receptor is FTY720 (fingolimod), an immunosuppressive agent currently in clinical trials (Martini et al, Expert Opin. Investig. Drugs, 16:505-518, 2007). FTY720 acts as a prodrug which is phosphorylated in vivo; the phosphorylated derivative is an agonist for S1P1, S1P3, S1P4, and S1P5 receptors (but not the S1P2 receptor) (Chiba, Pharmacology & Therapeutics, 108:308-319, 2005). FTY720 has been shown to rapidly and reversibly induce lymphopenia (also referred to as peripheral lymphocyte lowering (PLL); Hale et al, Bioorg. Med. Chem. Lett., 14:3351-3355, 2004). This is attended by clinically useful immunosuppression by virtue of sequestering T- and B-cells in secondary lymphoid tissue (lymph nodes and Peyer's patches) and thus apart from sites of inflammation and organ grafts (Rosen et al., Immunol. Rev., 195:160-177, 2003; Schwab et al, Nature Immunol., 8:1295-1301, 2007).
In clinical trials, FTY720 elicited an adverse event (i.e., transient asymptomatic bradycardia) due to its agonism of the S1P3 receptor (Budde et al., J. Am. Soc. Nephrol., 13:1073-1083, 2002; Sanna et al., J. Biol. Chem., 279:13839-13848, 2004; Ogawa et al., BBRC, 361:621-628, 2007).
FTY720 has been reported to have therapeutic efficacy in at least: a rat model for autoimmune myocarditis and a mouse model for acute viral myocarditis (Kiyabayashi et al., J. Cardiovasc. Pharmacol., 35:410-416, 2000; Miyamoto et al., J. Am. Coll. Cardiol., 37:1713-1718, 2001); mouse models for inflammatory bowel disease including colitis (Mizushima et al., Inflamm. Bowel Dis., 10:182-192, 2004; Deguchi et al., Oncology Reports, 16:699-703, 2006; Fujii et al., Am. J. Physiol. Gastrointest. Liver Physiol., 291:G267-G274, 2006; Daniel et al., J. Immunol., 178:2458-2468, 2007); a rat model for progressive mesangioproliferative glomerulonephritis (Martini et al., Am. J. Physiol. Renal Physiol., 292:F1761-F1770, 2007); a mouse model for asthma, suggested to be primarily through the S1P1 receptor on the basis of work using the S1P1 receptor agonist SEW2871 (Idzko et al, J. Clin. Invest., 116:2935-2944, 2006); a mouse model for airway inflammation and induction of bronchial hyperresponsiveness (Sawicka et al., J. Immunol., 171; 6206-6214, 2003); a mouse model for atopic dermatitis (Kohno et al., Biol. Pharm. Bull., 27:1392-1396, 2004); a mouse model for ischemia-reperfusion injury (Kaudel et al., Transplant. Proc, 39:499-502, 2007); a mouse model for systemic lupus erythematosus (SLE) (Okazaki et al., J. Rheumatol., 29:707-716, 2002; Herzinger et al, Am. J. Clin. Dermatol., 8:329-336, 2007); rat models for rheumatoid arthritis (Matsuura et al., Int. J. Immunopharmacol., 22:323-331, 2000; Matsuura et al., Inflamm. Res., 49:404-410, 2000); a rat model for autoimmune uveitis (Kurose et al., Exp. Eye Res., 70:7-15, 2000); mouse models for type I diabetes (Fu et al, Transplantation, 73:1425-1430, 2002; Maki et al., Transplantation, 74:1684-1686, 2002; Yang et al., Clinical Immunology, 107:30-35, 2003; Maki et al., Transplantation, 79:1051-1055, 2005); mouse models for atherosclerosis (Nofer et al., Circulation, 115:501-508, 2007; Keul et al., Arterioscler. Thromb. Vasc. Biol., 27:607-613, 2007); a rat model for brain inflammatory reaction following traumatic brain injury (TBI) (Zhang et al., J. Cell. Mol. Med., 11:307-314, 2007); and mouse models for graft coronary artery disease and graft-versus-host disease (GVHD) (Hwang et al., Circulation, 100:1322-1329, 1999; Taylor et al., Blood, 110:3480-3488, 2007). In vitro results suggest that FTY720 may have therapeutic efficacy for β-amyloid-related inflammatory diseases including Alzheimer's disease (Kaneider et al., FASEB J., 18:309-311, 2004). KRP-203, an S1P receptor agonist having agonist activity on the S1P1 receptor, has been reported to have therapeutic efficacy in a rat model for autoimmune myocarditis (Ogawa et al., BBRC, 361:621-628, 2007). Using the S1P1 receptor agonist SEW2871, it has been shown that agonism of endothelial S1P1 receptors prevents proinflammatory monocyte/endothelial interactions in type I diabetic vascular endothelium (Whetzel et al., Circ. Res., 99:731-739, 2006) and protects the vasculature against TNFα-mediated monocyte/endothelial interactions (Bolick et al., Arterioscler. Thromb. Vasc. Biol., 25:976-981, 2005).
Additionally, FTY720 has been reported to have therapeutic efficacy in experimental autoimmune encephalomyelitis (EAE) in rats and mice, a model for human multiple sclerosis (Brinkmann et al., J. Biol. Chem., 277:21453-21457, 2002; Fujino et al., J. Pharmacol. Exp. Ther., 305:70-77, 2003; Webb et al., J. Neuroimmunol., 153:108-121, 2004; Rausch et al., J. Magn. Reson. Imaging, 20:16-24, 2004; Kataoka et al., Cellular & Molecular Immunology, 2:439-448, 2005; Brinkmann et al., Pharmacology & Therapeutics, 115:84-105, 2007; Baumruker et al., Expert Opin. Investig. Drugs, 16:283-289, 2007; Balatoni et al., Brain Research Bulletin, 74:307-316, 2007). Furthermore, FTY720 has been found to have therapeutic efficacy for multiple sclerosis in clinical trials. In Phase II clinical trials for relapsing-remitting multiple sclerosis, FTY720 was found to reduce the number of lesions detected by magnetic resonance imaging (MRI) and clinical disease activity in patients with multiple sclerosis (Kappos et al., N Engl. J. Med., 355:1124-1140, 2006; Martini et al., Expert Opin. Investig. Drugs, 16:505-518, 2007; Zhang et al., Mini-Reviews in Medicinal Chemistry, 7:845-850, 2007; Brinkmann, Pharmacology & Therapeutics, 115:84-105, 2007). FTY720 is currently in Phase III studies of remitting-relapsing multiple sclerosis (Brinkmann, Pharmacology & Therapeutics, 115:84-105, 2007; Baumruker et al., Expert. Opin. Investig. Drugs, 16:283-289, 2007; Dev et al., Pharmacology and Therapeutics, 117:77-93, 2008).
Recently, FTY720 has been reported to have anti-viral activity. Specific data has been presented in the lymphocytic choriomeningitis virus (LCMV) mouse model, wherein the mice were infected with either the Armstrong or the clone 13 strain of LCMV (Premenko-Lanier et al., Nature, 454, 894, 2008).
FTY720 has been reported to impair migration of dendritic cells infected with Francisella tularensis to the mediastinal lymph node, thereby reducing the bacterial colonization of it. Francisella tularensis is associated with tularemia, ulceroglandular infection, respiratory infection and a typhoidal disease (E. Bar-Haim et al, PLoS Pathogens, 4(11): e1000211. doi:10.1371/journal.ppat.1000211, 2008).
It has also been recently reported that a short-term high dose of FTY720 rapidly reduced ocular infiltrates in experimental autoimmune uveoretinitis. When given in the early stages of ocular inflammation, FTY720 rapidly prevented retinal damage. It was reported to not only prevent infiltration of target organs, but also reduce existing infiltration (Raveney et al., Arch. Ophthalmol. 126(10), 1390, 2008).
It has been reported that treatment with FTY720 relieved ovariectomy-induced osteoporosis in mice by reducing the number of mature osteoclasts attached to the bone surface. The data provided evidence that S1P controled the migratory behaviour of osteoclast precursors, dynamically regulating bone mineral homeostasis (Ishii et al., Nature, advance online publication, 8 Feb. 2009, doi:10.1038/nature07713).
Agonism of the S1P1 receptor has been implicated in enhancement of survival of oligodendrocyte progenitor cells. Survival of oligodendrocyte progenitor cells is a required component of the remyelination process. Remyelination of multiple sclerosis lesions is considered to promote recovery from clinical relapses. (Miron et al., Ann. Neurol., 63:61-71, 2008; Coelho et al., J. Pharmacol. Exp. Ther., 323:626-635, 2007; Dev et al., Pharmacology and Therapeutics, 117:77-93, 2008). It also has been shown that the S1P1 receptor plays a role in platelet-derived growth factor (PDGF)-induced oligodendrocyte progenitor cell mitogenesis (Jung et al., Glia, 55:1656-1667, 2007).
Agonism of the S1P1 receptor has also been reported to mediate migration of neural stem cells toward injured areas of the central nervous system (CNS), including in a rat model of spinal cord injury (Kimura et al., Stem Cells, 25:115-124, 2007).
Agonism of the S1P1 receptor has been implicated in the inhibition of keratinocyte proliferation (Sauer et al., J. Biol. Chem., 279:38471-38479, 2004), consistent with reports that S1P inhibits keratinocyte proliferation (Kim et al., Cell Signal, 16:89-95, 2004). The hyperproliferation of keratinocytes at the entrance to the hair follicle, which can then become blocked, and an associated inflammation are significant pathogenetic factors of acne (Koreck et al., Dermatology, 206:96-105, 2003; Webster, Cutis, 76:4-7, 2005).
FTY720 has been reported to have therapeutic efficacy in inhibiting pathologic angiogenesis, such as that as may occur in tumor development. Inhibition of angiogenesis by FTY720 is thought to involve agonism of the S1P1 receptor (Oo et al., J. Biol. Chem., 282; 9082-9089, 2007; Schmid et al., J. Cell Biochem., 101:259-270, 2007). FTY720 has been reported to have therapeutic efficacy for inhibiting primary and metastatic tumor growth in a mouse model of melanoma (LaMontagne et al., Cancer Res., 66:221-231, 2006). FTY720 has been reported to have therapeutic efficacy in a mouse model for metastatic hepatocellular carcinoma (Lee et al., Clin. Cancer Res., 11:84588466, 2005).
It has been reported that oral administration of FTY720 to mice potently blocked VEGF-induced vascular permeability, an important process associated with angiogenesis, inflammation, and pathological conditions such as sepsis, hypoxia, and solid tumor growth (T Sanchez et al, J. Biol. Chem., 278(47), 47281-47290, 2003).
Cyclosporin A and FK506 (calcineurin inhibitors) are drugs used to prevent rejection of transplanted organs. Although they are effective in delaying or suppressing transplant rejection, classical immunosuppressants such as cyclosporin A and FK506 are known to cause several undesirable side effects including nephrotoxicity, neurotoxicity, β-cell toxicity and gastrointestinal discomfort. There is an unmet need in organ transplantation for an immunosuppressant without these side effects which is effective as a monotherapy or in combination with a classical immunosuppressant for inhibiting migration of, e.g., alloantigen-reactive T-cells to the grafted tissue, thereby prolonging graft survival.
FTY720 has been shown to have therapeutic efficacy in transplant rejection both as a monotherapy and in synergistic combination with a classical immunosuppressant, including cyclosporin A, FK506 and RAD (an mTOR inhibitor). It has been shown that, unlike the classical immunosuppressants cyclosporin A, FK506 and RAD, FTY720 has efficacy for prolonging graft survival without inducing general immunosuppression, and this difference in drug action is believed to be relevant to the synergism observed for the combination (Brinkmann et al., Transplant Proc., 33:530-531, 2001; Brinkmann et al., Transplantation, 72:764-769, 2001).
Agonism of the S1P1 receptor has been reported to have therapeutic efficacy for prolonging allograft survival in mouse and rat skin allograft models (Lima et al., Transplant Proc., 36:1015-1017, 2004; Yan et al., Bioorg. & Med. Chem. Lett., 16:3679-3683, 2006). FTY720 has been reported to have therapeutic efficacy for prolonging allograft survival in a rat cardiac allograft model (Suzuki et al., Transpl. Immunol., 4:252-255, 1996). FTY720 has been reported to act synergistically with cyclosporin A to prolong rat skin allograft survival (Yanagawa et al., J. Immunol., 160:5493-5499, 1998), to act synergistically with cyclosporin A and with FK506 to prolong rat cardiac allograft survival, and to act synergistically with cyclosporin A to prolong canine renal allograft survival and monkey renal allograft survival (Chiba et al., Cell Mol Biol., 3:11-19, 2006). KRP-203, an S1P receptor agonist has been reported to have therapeutic efficacy for prolonging allograft survival in a rat skin allograft model and both as monotherapy and in synergistic combination with cyclosporin A in a rat cardiac allograft model (Shimizu et al., Circulation, 111:222-229, 2005). KRP-203 also has been reported to have therapeutic efficacy in combination with mycophenolate mofetil (MMF; a prodrug for which the active metabolite is mycophenolic acid, an inhibitor of purine biosynthesis) for prolonging allograft survival both in a rat renal allograft model and in a rat cardiac allograft model (Suzuki et al., J Heart Lung Transplant, 25:302-209, 2006; Fujishiro et al., J. Heart Lung Transplant, 25:825-833, 2006). It has been reported that an agonist of the S1P1 receptor, AUY954, in combination with a subtherapeutic dose of RAD001 (Certican/Everolimus, an mTOR inhibitor) can prolong rat cardiac allograft survival (Pan et al., Chemistry & Biology, 13:1227-1234, 2006). In a rat small bowel allograft model, FTY720 has been reported to act synergistically with cyclosporin A to prolong small bowel allograft survival (Sakagawa et al., Transpl. Immunol., 13:161-168, 2004). FTY720 has been reported to have therapeutic efficacy in a mouse islet graft model (Fu et al., Transplantation, 73:1425-1430, 2002; Liu et al., Microsurgery, 27:300-304; 2007) and in a study using human islet cells to evidence no detrimental effects on human islet function (Truong et al., American Journal of Transplantation, 7:2031-2038, 2007).
FTY720 has been reported to reduce the nociceptive behavior in the spared nerve injury model for neuropathic pain which does not depend on prostaglandin synthesis (O. Costu et al, Journal of Cellular and Molecular Medicine 12(3), 995-1004, 2008).
FTY720 has been reported to impair initiation of murine contact hypersensitivity (CHS). Adoptive transfer of immunized lymph node cells from mice treated with FTY720 during the sensitization phase was virtually incapable of inducing CHS response in recipients (D. Nakashima et al., J. Investigative Dermatology (128(12), 2833-2841, 2008).
It has been reported that prophylactic oral administration of FTY720 (1 mg/kg, three times a week), completely prevented the development of experimental autoimmune myasthenia gravis (EAMG) in C57BL/6 mice (T. Kohono et al, Biological & Pharmaceutical Bulletin, 28(4), 736-739, 2005).
In one embodiment, the present invention encompasses compounds which are agonists of the S1P1 receptor having selectivity over the S1P3 receptor. The S1P3 receptor, and not the S1P1 receptor, has been directly implicated in bradycardia (Sanna et al., J. Biol. Chem., 279:13839-13848, 2004). An S1P1 receptor agonist selective over at least the S1P3 receptor has advantages over current therapies by virtue of an enhanced therapeutic window, allowing better tolerability with higher dosing and thus improving efficacy as therapy. The present invention encompasses compounds which are agonists of the S1P1 receptor and which exhibit no or substantially no activity for bradycardia.
S1P1 receptor agonists are useful to treat or prevent conditions where suppression of the immune system or agonism of the S1P1 receptor is in order, such as diseases and disorders mediated by lymphocytes, transplant rejection, autoimmune diseases and disorders, inflammatory diseases and disorders, and conditions that have an underlying defect in vascular integrity or that relate to angiogenesis such as may be pathologic.
In one embodiment, the present invention encompasses compounds which are agonists of the S1P1 receptor having good overall physical properties and biological activities and having an effectiveness that is substantially at least that of prior compounds with activity at the S1P1 receptor.
Citation of any reference throughout this application is not to be construed as an admission that such reference is prior art to the present application.